those are what abdominal MUSCLES look like. when they get big enough, they stick out like a gut.

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I didn't watch the video but what I suspect you're seeing is a guy who has taken to much Human Growth Hormone and their internal organs start growing too. It is very common among professional bodybuilders who abuse this HGH. The guy can be super lean but it looks like he has a beer belly at times because it sticks out so much.